The present invention relates to the employment of solutions or uniform blends of polyimide having condensed units selected from, ##STR1## a mixture thereof, referred to hereinafter as "SDAN" units or bis(4-aminophenylsulfonyl) units and "DAPI" units, or diaminophenylindane units. More particularly, the present invention relates to certain polyimide compositions useful for providing chip adhesives, or laminating or film adhesives for making multi-chip high density interconnect (HDI) integrated circuit packaging configurations.
Prior to the present invention as shown by Eichelberger et al, U.S. Pat. No. 4,783,695, various resins, such as Ultem.RTM. polyetherimide and epoxy resins were used to bond chips to various substrate, such as ceramic, alumina, metal, glass or plastic. In this HDI approach, successive layers of dielectric and patterned metal are fabricated over the bare chips on a ceramic substrate to provide a completed electronic device. In addition to bonding chips, thermoplastic adhesives have been used to bond films, such as Kapton.RTM. resin to the applied chips.
When fabricating HDI configurations, polymers with different Tg's or softening points are required, because the temperature for bonding films over the substrate and chips must be kept below the Tg of the chip adhesive to prevent inadvertent chip movement during manufacture. Other important characteristics needed by polymers used in HDI applications are good adhesion to electronic components and metal, appropriate optical absorption for laser fabrication of via holes, and the ability to be easily removed.
In U.S. Pat. No. 4,820,781, Policastro et al, blends of silicone copolymer and polyetherimide are shown having Tg's in the range from about 190.degree. C. to 210.degree. C. Additional silicone polyimides and polyimide siloxanes are shown by Policastro et al, U.S. Pat. No. 4,826,916 and U.S. Pat. No. 4,795,680 incorporated herein by reference which are useful as coating materials in electronic applications, or as dielectric or passivating layers in semiconductor devices.
Although, Ultem.RTM. polyetherimide having a Tg of 217.degree. C. has been found useful for fabricating multi-chip integrated circuits, thermoplastic resins with higher Tg's, such as 220.degree. C. to 320.degree. C. are constantly being sought to avoid inadvertent chip and/or film removal when repairing such HDI electronic packaging.
Even though polyimides having Tg's as high as 320.degree. C. are available in the construction of HDI circuitry, they must be applied as a solution. Phenolic solvents can be used in particular instances, but their use is limited due to their acidic properties which halve a deleterious effect on the delicate circuit components. As a result, the need exists for additional resins having appropriate physical, electrical and chemical characteristics for use in electronic packaging.